#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
	int server_sockfd;
	int len;
	int sin_size;
	struct sockaddr_in my_addr;			  // 服务器网络地址结构体
	struct sockaddr_in remote_addr;		  // 客户端网络地址结构体
	char buf[BUFSIZ];					  // 数据传送的缓冲区
	memset(&my_addr, 0, sizeof(my_addr)); // 数据初始化--清零
	my_addr.sin_family = AF_INET;		  // 设置为IP通信
	my_addr.sin_addr.s_addr = INADDR_ANY; // 服务器IP地址--允许连接到所有本地地址上
	my_addr.sin_port = htons(8000);		  // 服务器端口号

	/*创建服务器端套接字--IPv4协议，面向无连接通信，UDP协议*/
	if ((server_sockfd = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
	{
		perror("socket");
		return 1;
	}

	/*将套接字绑定到服务器的网络地址上*/
	if (bind(server_sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) < 0)
	{
		perror("bind");
		return 1;
	}
	sin_size = sizeof(struct sockaddr_in);
	printf("waiting for a packet...\n");

	while (1)
	{
		/*接收客户端的数据并将其发送给客户端--recvfrom是无连接的*/
		if ((len = recvfrom(server_sockfd, buf, BUFSIZ, 0, (struct sockaddr *)&remote_addr, (socklen_t *)&sin_size)) < 0)
		{
			perror("recvfrom");
			return 1;
		}
		printf("received packet from %s:%d\n", inet_ntoa(remote_addr.sin_addr), ntohs(remote_addr.sin_port));
		buf[len] = '\0';
		printf("contents: %s\n", buf);

		len = sendto(server_sockfd, buf, strlen(buf), 0, (struct sockaddr *)&remote_addr, sizeof(struct sockaddr));
	}

	close(server_sockfd);
	return 0;
}
